Offset printing employs an arrangement of cooperating cylinders, including a plate cylinder, a blanket cylinder, and an impression cylinder, mounted for rotation in a printing press. Anti-friction roller bearings are normally provided to support the journals of these cylinders and allow ease of rotation. Typically, three-ring roller bearings, such as those shown in DE-OS 1,400,391 and DE-OS 3,643,295, having bearing rings which are disposed radially one inside the other and are held axially and/or radially relative to one another with rows of rolling bearings disposed therebetween, are employed for this purpose.
Oftentimes, it is desirable to disengage the blanket cylinder from the other cylinders. Thus, the bearings for the journals of blanket cylinders in printing machines have been designed so as to allow the blanket cylinder to be eccentrically adjusted to engage and disengage from the other cylinders. For eccentric adjustment or displacement of the cylinders, these roller bearings are provided with an eccentric intermediate ring, i.e. a ring provided with inner and outer raceways eccentric to one another, with a throw-off lever attached.
Printing presses additionally require that roller bearings be completely free from radial play and of sufficiently rigidly construction in the axial direction to prevent printing errors which may occur due to rotational deviations. A complication exists in that the weight of the cylinder tends to cause errors in the alignment of the roller bearing in the bores of the supporting press frame as a result of deflection of the cylinder and tilting of the cylinder journals. It is known in the prior art from DE-0S 3,324,811 to provide separate radial and axial bearings for anti-friction mounting of the journals of blanket cylinders in printing machines in order to increase the rigidity of the mounting. Further, to compensate for alignment errors, it is known from DE-OS 3,635,569 to form at least the outer axial contour of an outer bearing ring of a cylindrical plain bearing as an arcuate swing surface, the outer ring of the outer bearing and an inner ring of the inner bearing being eccentric so that axes of the double-eccentric plain bearings can automatically line up with the cylinder journals.
A general failing of the prior art is that it does not permit for compensation of the alignment errors of the bores in the printing press frame because the nominal bearing position is predetermined by its centering in the machine frame and its alignment to the journal is not guaranteed. Further, the prior art fails to provide a method for adequately radially prestressing these bearings to compensate for alignment errors or to provide a means for automatically aligning the bearing axis to the axis of the journal.